I am shure you have checked most of these settings, but just as a hint (from a PC user who uses running systems for 3 or 5 years to avoid such hassles!)

- do you have used the same RAW files and the same DPP version on both machines? Between 40D and 600D there is a factor 4 or 5 in processing speed on my old 3GHz P-IV Desktop

- how many cores do both notebooks have? What is the max CPU clock (not the only criterion but you have two systems with similar CPU architecture, so it should scale)? As far as I know DPP is multithreaded, meaning that it can use all the cores of your system and it profits from CPU speed too.

- does the graphics card use hardware acceleration etc.?

- check the energy saving settings of the notebooks: Set it to maximum performance at least if it is connected to a power plug